Abstract
Purpose :
To estimate the effect of achieving target pressure intraocular pressure (IOP) values on retinal nerve fiber layer (RNFL) worsening compared to mean deviation (MD) worsening in a treated clinical population.
Methods :
A total of 7,410 eyes from 4,229 patients with manifest or suspect glaucoma followed at a tertiary practice were studied. Included eyes had at least 5 reliable optical coherence tomography (OCT) or visual field (VF) studies and 5 concurrent IOP measurements over time. Target IOP was defined by the treating clinician on the 1st or 2nd visit. Baseline disease severity was defined by the MD of the first reliable VF. The primary independent variables were mean target difference (measured IOP – target IOP) or mean IOP over follow-up. The primary dependent variable was the slope of RNFL or MD over time (μm/year or dB/year). We used both a univariate linear regression model and a multivariate linear mixed effects model to estimate the effect of mean target difference and mean IOP on RNFL and MD slope, adjusting for potential confounding variables. The multivariate model additionally included interaction terms for severity, and spline knots for IOPs above and below the target.
Results :
The univariate linear regression model demonstrated a 1 mmHg increase in target difference and mean IOP results in a –0.025 (95% CI: –0.036 to –0.013) and a –0.048 (–0.060 to –0.037) effect on RNFL slope, respectively. Meanwhile, a 1 mmHg increase in target difference and mean IOP resulted in a –0.018 (–0.024 to –0.013) and –0.001 (–0.005 to 0.007) effect on the MD slope, respectively. Eyes with moderate glaucoma experienced more pronounced effects of each mmHg increase in target difference on both RNFL and MD slopes. The multivariate model’s results did not change the main results of the univariate analysis.
Conclusions :
Both our univariate and our multivariate model indicate that, in patients undergoing treatment at a tertiary care glaucoma center, failing to achieve target pressure was more strongly associated with functional (VF) loss than the absolute level of IOP. However, failing to achieve target pressure and absolute level of IOP had similar effects on structural (OCT) loss.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.